1. Technical Field
This invention relates to methods of making holograms and, more particularly, to methods of making holograms on thin substrates suitable for use on automotive windows.
2. Discussion
There exists several potential application for holograms on transparent surfaces. One such application would be the use of a hologram on or in a car windshield.
Holograms on thin substrates, whether plastic or glass, are difficult to form, especially if the photosensitive material is a low sensitivity material such as dichromated gelatin. One possible technique for obtaining holographic projections on thin transparent substrates would be to bold the substrate between two thicker transparent substrates during exposure. One disadvantage with this technique is that during later processing steps the thin substrate would be unprotected and the fragile glass could be damaged. An alternative technique would be to use a plastic film base which would survive the processing steps but it would not provide the same protection as glass laminated onto the windshield. Other techniques might involve transferring just the photosensitive film onto the windshield. Here the disadvantage is lack of environmental protection that the glass provides.